Reforestation in sloping terrain is an important measure for soil erosion control and sustainable watershed management. The mechanical stability of such reforested stands, however, can be low due to a strong asymmetric shape of tree crowns. We investigated how neighbourhood tree species richness, neighbourhood pressure, tree height, and slope inclination affect crown asymmetry in a large-scale plantation biodiversity-ecosystem functioning experiment in subtropical China (BEF-China) over eight years. We took the advantage of terrestrial laser scanning (TLS) measurements, which provide non-destructive, high-resolution data of tree structure without altering tree interactions. Neighbourhood species richness significantly reduced crown asymmetry, and this effect became stronger at steeper slopes. Our results suggest that tree diversity promotes the mechanical stability of forest stands in sloping terrain and highlight the importance of TLS-data for a comprehensive understanding of the role of tree diversity in modulating crown interactions in mixed-species forest plantations.
Figure 1 Graphic representation of (a) crown displacement, where the crown projection area is shown in grey, the centre is represented as a red dot, and the crown displacement is represented as a red arrow. In green is the alpha shape representation of an individual tree; (b) microtopography, showing in brown the terrain, in green the representation of an individual tree, and in red the vector of microtopography; and (c) neighbourhood pressure, showing the crown projection area of the target tree (with a black outline) and its direct neighbours.
Figure 2 Differences in the strength of the effects of (a) target tree height and (b) neighbourhood pressure (square root-transformed) on crown displacement (square root-transformed).
Figure 3 (a) Effects of microtopography (MT) on crown displacement (square root-transformed) with varying levels of neighbourhood tree species richness (NSR). (b) Relative changes (%) in crown displacement between conspecific neighbourhoods (NSR: 0) and heterospecific neighbourhoods (NSR: 1–5).
Maria D. Perles-Garcia
*, Matthias Kunz, Andreas Fichtner, Nora Meyer, Werner Härdtle and Goddert von Oheimb. 2022. Neighbourhood species richness reduces crown asymmetry of subtropical trees in sloping terrain. Remote Sensing. 14(6): 1441. https://doi.org/10.3390/rs14061441.